We consider a real-time multi-server system with identical servers (such as machine controllers,
unmanned aerial vehicles,overhearing devices, etc.) which can be adjusted/programmed for different types of
activities (e.g. active or passive). This system provides a service for real-time jobs arriving via several channels
(such as assembly lines, surveillance regions, communication channels, etc.) and involves maintenance. We
perform the worst case analysis of the system working under maximum load with preemptive priorities assigned
for servers of different activity type. We consider a system with separate queue to each channel. Two models
with ample maintenance teams and shortage of maintenance teams are treated. We provide analytical
approximations of steady state probabilities for these real-time systems and check their quality.